High service temperature pressure sensitive device

ABSTRACT

Rupture discs are combined with cooling means to provide high service temperature pressure sensitive devices.

United States Patent [191 Didycz et a1.

[451 Dec. 17, 1974 1 HIGH SERVICE TEMPERATURE PRESSURE SENSITIVE DEVICE[75] Inventors: William J. Didycz, Whitehall Borough; Almon D. Seabury,Hampton Twp., Allegheny County,

both of Pa.

[73] Assignee: United States Steel Corporation, Pittsburgh, Pa.

[22] Filed: Apr. 25, 1973 [21] Appl. No.: 354,609

Related US Application Data [62] Division of Ser. No. 133,938, April 14,1971, Pat.

[52] US. Cl 165/1, 137/68, 137/797, 165/53, 220/27, 220/89 A [51] Int.Cl. F24h 13/00 [58] Field of Search 137/68, 340, 334, 797,

I 137/69, 71; 220/89 A, 44 C, 44 R, 27; 176/38, 87; 165/1, 138, 47, 53

Primary Examiner-Albert W. Davis, Jr. Assistant Examiner-S. J. RichterAttorney, Agent, or Firm-David S, Urey [5 7] ABSTRACT Rupture discs arecombined with cooling means to provide high service temperature pressuresensitive devices.

3 Claims, 3 Drawing Figures HIGH SERVICE TEMPERATURE PRESSURE SENSITIVEDEVICE This application is a divisional application of U.S. PatentApplication Ser. No. 133,938 filed Apr. 14, 1971, now US. Pat. No.3,780,793, granted on Dec. 25, 1973 and assigned to the assignee of thepresent application.

BACKGROUND OF THE INVENTION Many pressure servicing requirements forvessels are handled by devices known as rupture discs which have astheir primary element a membrane that will burst within a small range ofa specified pressure and so prevent over-pressure in the vessel.Usually, the rupture disc, covering an opening in the vessel, is heldbetween flanges.

A rupture disc has fewer moving parts than other pressure releasingdevices such as safety valves. The outstanding characteristics ofrupture discs are fast action and large capacity. The absence of avalving mechanism or seat also makes them particularly advantageous forsticky or gummy materials.

There are two basic classes of rupture discs metallic and non-metallic.Metallic discs can be made from a variety of materials such as aluminum,copper, stainless steel, etc. Special corrosion-resistant applicationsmight require lining the disc with fluorocarbons or fluorohalocarbons.To obtain economical disc life, it is imperative that the rupture discnot be exposed to very high temperatures since all pre-formed discmaterials have a reduction in strength when exposed to an elevatedtemperature. There are elevated temperature limitations beyond which thevarious materials are not recommended for use in rupture discs. Forexample,

aluminum is not recommended for use at temperatures over approximately250F. By using special alloys such as lnconel or by the use of acomposite disc of two or more metals, the service temperature of thediscs may be increased to approximately 1,000F. However, operating therupture disc at such high temperatures increases the tendency towardmetal creep and necessitates a somewhat wider margin between operatingand rupture pressures than necessary at lower temperatures in order toachieve maximum service life.

Thus, there exists a need for a high service temperature (over l,0OF)pressure sensitive device providing the advantages associated withrupture discs. It is one object of this invention to provide such adevice.

SUMMARY OF THE INVENTION Accordingly, we have now found that bycombining an ordinary rupture disc with a cooling means for flowing acooling liquid across the outer surface of the rupture disc, we canincrease the service temperature of the disc to over l,O0OF. In the highservice temperature pressure sensitive device of our invention (a rupture disc), a low service temperature pressure sensitive device (lessthan 500F) is combined with a cooling liquid means disposed adjacent tothe rupture disc for directing a cooling liquid on the rupture disc. Wethereby obtain the advantages of using rupture discs in environmentswhere the temperature far exceeds the service temperature of the rupturedisc.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a top view of our devicemounted on a pressure vessel;

FIG. 2 is a cross-sectional view of our device mounted on a pressurevessel taken along the line ll-lI of FIG. 1 in the direction of thearrows; and

FIG. 3 is a vertical sectional view of the-means as shown in FIG. 1 ofthe complete cooling means taken along a line similar to line llII ofFIG. 1 in the direction of the arrows and showing a larger amount ofcooling fluid than in FIG. 2.

DETAILED DESCRIPTION Referring to FIGS. 2 and 3, the pressure vessel I(FIGS. 1, 2) has a flanged opening 2 on its upper surface. A rupturedisc 3 (FIGS. 1-3) is mounted'over the opening 2. A container 4 (FIGS.1-3) for liquids is mounted over the rupture disc 3. The container 4 forliquids and the rupture disc 3 are secured to the flanged opening 2 inthe wall of the pressure vessel 1 by means of bolts 5. An inlet port 6,for the entry of cooling liquid, and an outlet port 7, for the exit ofcooling liquid, are provided in the wall of the container 4 for liquids,for the entry and exit of cooling liquid 8.

In FIG. 3, a cross sectional view of a preferred embodiment of ourinvention is depicted. An inlet port 6, for the entry of cooling liquid8, is provided in the wall of the container 4 for liquid, at a pointrelatively near the bottom of said container 4 for liquids. An exit port7, for the exit of cooling liquid 8, is provided in the wall of thecontainer for liquids, at a point relatively near the top of saidcontainer 4 for liquids.

Our high service temperature pressure sensitive device is composed of l)a rupture disc 3, and 2) a cooling liquid means. The rupture disc 3 isfastened over an opening in a wall of a pressure vessel 1 and thecooling liquid 8 is maintained on the outer surface of the rupture disc3. The rupture disc 3 may be made of any conventional material, forexample, chromium, copper, silver, nickel, Monel, lnconel or 347 or 316stainless steel. Non-metallic rupture discs may also be used, as forexample, discs fabricated of thermoplastic materials such aspolystyrenes, polyfluorocarbons, nylons, acetals, polycarbonates, etc.or of other non-metallic materials. The rupture disc 3 may be composedof a single material or it may be a laminate. Recommended maximumservice temperature for rupture discs 3 of these materials varies widelybut is 250F or below except for nickel, Monel, lnconel or 347 or 316stainless steels which have service temperatures of up to 400F. As thesetemperatures are approached or exceeded, the tendency toward metal creepis increased and a reduction in strength occurs. Thus, rupture discs 3which are recommended for use at for example, percent of rupturepressure at ambient temperature, are recommended for use at only about50 percent or less of rupture pressure at higher temperatures. As anexample of the lowering of rupture pressure with temperature, astainless steel rupture disc having a rupture pressure of 500 psig at72F has a rupture pressure of about 425 psig at 200F, about 355 psig at400F and about 340 psig at 600F. Also, the service life of the discs 3decreases rapidly as the upper limit of recommended service temperatureis approached or exceeded.

Our invention, by applying liquid cooling means to the outer surface ofthe disc 3, allows the use of rupture discs 3 in environments farexceeding their usual service temperature while retaining the discstrength and long service life. The liquid cooling means maintains thetemperature of the disc 3 far below that of its environment. Inconsequence, corrosive materials present in gaseous form in theatmosphere of the pressure vessel 1 very often condense on the innerface of the rupture disc 3. To preclude corrosion of the rupture disc 3,we have found it highly advantageous to coat the inner surface andpreferably both surfaces of the disc 3 with a corrosion retardingsubstance, of which solid polyfluorocarbons such as Teflon (a registeredtrade mark of du Font) and polyfluorohalocarbons are preferred examples.

The rupture disc 3 is attached to the wall of the pressure vessel 1 in apressure tight relationship. We have found that mounting the rupturedisc 3 by means of bolts and gaskets is a simple, convenient and usefulmethod; however, other mounting means may also be used.

The type of pressure vessel 1 on which our high service temperaturepressure sensitive device may be used may vary widely. Our devices haveprimary application where the environment within the pressure vessel 1is above the service temperature of ordinary rupture discs 3. Thus, wewould contemplate use of our devices in incinerators, autoclaves andchemical process reactors. These examples are non-limiting however asthe devices of our invention may be used in any pressure vessel 1wherein the pressure is within the pressure range of available rupturediscs 3. The temperature environment of the pressure vessel 1 is not alimiting factor, as, by choice of appropriate cooling liquid and/or flowrate, our devices may accommodate any environment. it is contemplatedthat matter contacting the inner face of the rupture disc 3 would be atleast partially in the gaseous state, although in some instances theinner face of the disc 3 could be immersed in a liquid. Problemsinvolving heat transfer could arise, as could interference with chemicalreactions taking place in the pressure vessel 1, were the disc 3completely immersed in a liquid in the pressure vessel 1.

Liquid Cooling Means The liquid cooling means comprises a liquiddelivery means 6 and a means for maintaining the liquid 8 in contactwith the outer surface of the rupture disc 3. in a preferred embodimentof our invention, the delivery means is a pipe 6 and the means formaintaining the liquid in contact with the disc is a cylinder 4 mountedover the rupture disc 3. The means for maintaining the liquid in contactwith the disc may be any type of vented container 4. Ports 6, 7 may beprovided in the walls of the container 4 for the entry of cool and exitof hot liquid 8, or the liquid 8 may merely be allowed to overflow thetop of the container 4.

The cooling liquid 8 may be any liquid which is inert in the environmentin which it is to be used. Any of the common cooling liquids, such aswater, silicone and petroleum oils, glycols, such as ethylene glycol,etc., may be used. Water is the cooling liquid of choice in mostapplications because of its cheapness and safety.

The cooling liquid 8 may be recirculated after heat exchange to cool it,used until it becomes hot and then disposed of, or it may be maintainedover the disc 3 and allowed to boil away, care being taken toreplenishthe liquid 8 so that a body of liquid 8 is always maintained over thedisc 3.

The depth of the pool of cooling liquid 8 may vary within wide limitsbut should not be so deep as to exert a high opposing pressure on therupture disc 3. For

most applications, we have found that a depth of up to about 2 feet ofliquid 8 is suitable and that a depth of about 2 to 8 inches ispreferable. The depth of the liquid 8 could be greater than 2 feet butno new benefits are obtained by such an increase in depth and the timedelay is thereby increased.

if the cooling liquid 8 is allowed to boil, care must be taken that theboiling point of the cooling liquid 8 is within the range of theordinary service temperature of the rupture disc 3. We prefercontinuously to add cool liquid to the pool 8 over the rupture disc 3and to continuously withdraw hot liquid from the pool 8. By varying therate of addition of cool liquid 8 and withdrawal of hot liquid 8, it ispossible to obtain a temperature rise of not more than 5 or 10F. Whereit is most advantageous to use a small liquid flow, the temperature maybe allowed to rise or F or more up to either the boiling point of theliquid 8 or the upper limit of the service temperature of the disc 3.Where cooling liquid 8 is plentiful and cheap, a greater liquid flowrate may limit the temperature rise to only a few degrees above ambient.

Our invention is further illustrated by the following non-limitingexamples.

Example I A high service temperature pressure sensitive device of ourinvention was mounted on an incinerator 1 used to dispose of the wastegas from a phthalic anhydride plant. The incinerator operated at atemperature of 1,350F and a pressure of 0.67 psig. A rupture disc 3rated at 2 lb. i 03 psig and having a Teflon (trade mark) coating on itsinner surface was secured to a 30 inch diameter carbon steel cylinder 4having ports 6, 7 in its wall for the entry and exit of cooling liquid 8and a flange on its lower edge. The device was mounted over a flangedopening 2 of 30 inch diameter in the top of the incinerator l andsecured by means of 10% inch diameter bolts 5. The cylinder 4 was filledto a depth of 6 inches with water at a temperature of 60F. The flow rateof water to the cylinder 4 was 11 gallon/minute. The temperature of thewater was checked intermittently and was found to have reached, atequilibrium, a temperature of 70F. At the end of three months, thedevice was still in operation.

Example ll Procedure and materials as in Example 1 except that flow rateof water to the cylinder 4 was one-half gal Ion/minute. Watertemperature reached, at equilibrium, 180F.

We claim:

1. A method of increasing the service temperature of vented rupturediscs comprising maintaining a body of cooling liquid on the outersurface of said vented rupture disc.

2. A method of increasing the service temperature of vented rupturediscs comprising flowing a cooling liquid across the outer surface ofsaid vented rupture disc.

3. The method of claim 2 wherein the cooling liquid is water.

1. A method of increasing the service temperature of vented rupturediscs comprising maintaining a body of cooling liquid on the outersurface of said vented rupture disc.
 2. A method of increasing theservice temperature of vented rupture discs comprising flowing a coolingliquid across the outer surface of said vented rupture disc.
 3. Themethod of claim 2 wherein the cooling liquid is water.